Wifi sniffing in MacOS X Yosemite

Did you know that MacOS X 10.10 (Yosemite) now includes a packet sniffer? Useful for troubleshooting, or uh… other purposes. Just option-click on your Wi-Fi menu item and choose Open Wireless Diagnostics…

Ignore the opened window and just hit Command+6 to open the sniffer. Choose your channel and spectrum width and then click Start. You can capture as long as you want (or until you run out of disk space). If you’re not sure which channel space you want to sniff, hit Command+4 to open the scanner tool (available since 10.7).

You’ll find a timestamped .wcap file on your desktop that can be opened with Wireshark. I like to just open them with Console.app to stay local.